The economics of very large-scale integrated circuits (VLSI) or microcomputers are such that it is necessary to have long production runs in order to pay for the design costs of these elaborate systems. In order to use these large-scale chips, however, it is necessary to add a number of supplementary chips to adapt the large-scale chip to the particular application in question. The cost of installing these additional less sophisticated chips can be much greater than the cost of the complex chip, and it would be economically advantageous to have a special purpose complex chip. Unfortunately, special purpose complex chips also have high design costs which usually cannot be recouped over a short production run.
The problem addressed by this invention is: integrated circuit designers would like to reuse portions of the integrated circuit masks in several of a family of similar chips. The use of "random logic" (i.e., wires placed in an irregular manner) in connecting logical blocks on a chip has made it impractical to reuse some blocks because of the high cost of redoing the layout in order to connect the different logical blocks.
Some corporations have provided families of standard cells which are connected by means of computer aided design programs which perform the laborious function of providing the random logic.